Make strength of emmision independent from the surface brightness
With the Blender Internal renderer, it's not very easy, but it is doable.
The basic idea is to render the glowing ball twice, and composite the dimmer one over the brighter one.
Keep everything you have so far, but investigate how to render just the ball. The basics are, move it to its own layer and set up a second set of render layers that gives you only the ball, with nothing else in the scene at all.
More on Render Layers from the Manual:

Each Render Layer has an associated set of Scene Layers. Objects which are on one of the associated Scene Layers are shown in that Render Layer, as long as that Scene Layer is also visible.
Warning
Only the objects in visible Scene Layers will be rendered. So, if only Scene Layer 1 is visible and your Render Layer set specifies to render only Layers 2 and 3, nothing will be rendered.

Once you have those two renders happening at the same time, you will use the compositor to put the dimmer ball (that's all by itself) over top of the image that has everything in it. You'll use an Alpha Over node to combine the two.
More on the Alpha Over node in the Manual:

Use this node to layer images on top of one another. Alpha Over does not work on the colors of an image.


Doing this with Cycles is much simpler, but Cycles does not use the same materials as BI. You will have to make your materials again, as Cycles materials. That's why everything doesn't have any color when you just change renderers. Cycles is using a default gray material.